Rack and pinion elevator with at least two racks

ABSTRACT

A rack and pinion elevator system having at least two spaced racks and an elevator cage therebetween which carries at least one drive motor in driving engagement with each rack respectively, includes a transmission device such as a shaft which is connected to the elevator cage. At least two pinions, each engaging with a respective rack, are rigidly secured to the transmission means so that the pinions move along the racks together with the elevator cage to transfer driving forces via the transmission device from the less loaded to the more loaded side of the elevator cage thereby to substantially equalize the loads on the separate drive motors regardless of the position of the center of gravity of the load in the elevator cage.

United States Patent n 1 Johansson [11] 3,866,717 Feb. 18, 1975 MartinJohansson, Skelleftea, Sweden [73] Assignee: Linden-Alimak AB,Skelleftea,

Sweden [22] Filed: Feb. 23, 1973 [21] Appl. No.: 335,387

[75] Inventor:

[30] Foreign Application Priority Data 1,885,458 1l/1932 Maniscalco187/89 X 2,409,199 10/1946 Dunlop 2,514,498 7/1950 Kesler 2,609,1129/1952 McKenzie 187/19 X Primary Examiner-Evon C. Blunk AssistantExaminer-James L. Rowland Attorney, Agent, or FirmElliott 1. Pollock [57] ABSTRACT racks together, with the elevator cage to transfer drivingforces via the transmission device from the less loaded to the moreloaded side of the elevator cag'e thereby to substantially equalize theloads on the separate drive motors regardless of the position of thecenter of gravity of the load in the elevator cage.

4 Claims, 1 Drawing Figure Feb. 24, 1972 Sweden 2279/72 [52] U.S. Cl.187/19 [51] Int. Cl B66b ll/(M [58] Field of Search 187/19, 17, 6, 2, 1,8.59

[56] References Cited UNITED STATES PATENTS 467,096 l/1892 Harper 187/19X 568,576 9/1896 Lewis 187/78 571,864 11/1896 Parkhurst 187/19 763,9466/1904 Visco 187/19 1,844,133 2/1932 Maniscalo et al 187/89 X;llllllllllllllllllllllllllllll lllllllllT II IIlllllllllllllllllllllllllllllllllllllllllll lllllllllllllll 1 RACK ANDPINION ELEVATOR WITH AT LEAST TWO RACKS This invention relates to animproved drive arrangement for rack and pinion elevators.

ln rack and pinion elevators which, for example, climb on two racks, andwhich include an elevator cage which carries separate drive motors inseparate driving engagement with said two racks, the motors are loadeddifferently in response to the position of the load in the elevatorcage. When, for example, the center of gravity of the load is displacedin the elevator cage closer to one rack, then in a most unfavourablecase the motor or motors acting upon that one rack must take upsubstantially the entire load and, therefore, be dimensionedaccordingly, while the motor or motors acting upon the other rack runonly with a small load.

This inconvenience is eliminated by the improved drive arrangement ofthe present invention. By use of a transmission device which is carriedby the elevator cage and which extends between the two racks formovement along the racks with said elevator cage, the load isdistributed substantially equally on the drive motors, independently ofthe location of the load in the elevator cage.

According to a further development of the invention, the transmissiondevice also solves the problem of distributing the braking power from asafety means equally on the racks if the elevator cage should move at anexcessive speed. The desired distribution of braking power is achievedby coupling the safety means directly to the transmission means.

The FIGURE in the attached drawing shows in a schematic way anembodiment of a device according to the invention.

l designates an elevator cage, which is movable in the verticaldirection between two poles 2 and 3 and which is guided along the sameby tracks (not shown). The elevator cage is driven by separateelectromotors 4 engaging in pairs via gears 5 and pinions 6 each with arack 7 and 8 each secured on a pole. Two motors carried by the elevatorcage, thus, drive the cage along the rack 7 of one pole, and twoadditional motors carried by the elevator cage drive the cage along therack 8 of the other pole.

The transmission device which characterizes the present inventioncomprises a shaft 9 supported for rotation on the elevator cage. ltsends projecting from the cage are each rigidly fastened to a pinion l0engaging with the respective rack 7 and 8. The shaft 9 is provided todistribute the driving force equally on the motors. When, for example,in the FIGURE the load in the elevator cage is displaced to the right,the left-hand motors operate somewhat easier and lift their side of theelevator cage somewhat before the right-hand side. As

a result, driving force from the left-hand motors is partiallytransferred to the right-hand rack 8 through shaft 9 and thereby assiststhe right-hand motors.

The shaft 9 is also rigidly connected to a sprocket wheel 11, which viaa drive chain 12 is coupled to a sprocket wheel 13 of a safety means 14,which brakes the elevator cage via the shaft 9 when the cage exceeds apredetermined speed.

What I claim is:

1. A rack and pinion elevator system comprising a pair of horizontallyspaced, vertically extending racks having an elevator cage verticallymovable therebetween, drive means for selectively effecting movement ofsaid cage along said racks comprising at least two separate drive motorscarried by said cage, a first one of said drive motors having a firstoutput shaft carrying a first output pinion which is in drivingengagement with one only of said racks, a second one of said drivemotors having a second output shaft separate from said first outputshaft and carrying a second output pinion which is in driving engagementwith the other one only of said racks, and a transmission device carriedby said cage and extending between said racks for movement along saidracks with said elevator cage, said transmission device being separatedfrom said drive means and being responsive to off-center placement of aload in said cage for transferring forces from the less-loaded one ofsaid racks to the more-loaded one of said racks thereby to substantiallyequalize the loads on said two drive motors, said transmission devicecomprising an elongated third shaft spaced from each of said first andsecond shafts and extending between said pair of racks in parallelrelation to said first and second shafts, said third shaft being mountedfor rotation at a predetermined position on said elevator cage spacedfrom the location of said drive motors, the opposing ends of said thirdshaft respectively carrying third and fourth pinions which engage saidpair of racks respectively at positions spaced from each of said firstand second output pinions.

2. The system of claim 1 including selectively operable braking means inengagement withsaid transmission device for selectively applying brakingforces to each of said pair of racks via said transmission device,thereby to distribute said braking forces substantially equally to saidpair of racks.

3. The system of claim 2 wherein said braking means is operablyresponsive to the speed of movement of said elevator cage along saidracks.

4. The system of claim 1 including a sprocket wheel rigidly secured tosaid third shaft at a position between said third and fourth pinions,and a braking device connected via a drive chain to said sprocket wheelfor selectively braking said elevator cage.

1. A rack and pinion elevator system comprising a pair of horizontallyspaced, vertically extending racks having an elevator cage verticallymovable therebetween, drive means for selectively effecting movement ofsaid cage along said racks comprising at least two separate drive motorscarried by said cage, a first one of said drive motors having a firstoutput shaft carrying a first output pinion which is in drivingengagement with one only of said racks, a second one of said drivemotors having a second output shaft separate from said first outputshaft and carrying a second output pinion which is in driving engagementwith the other one only of said racks, and a transmission device carriedby said cage and extending between said racks for movement along saidracks with said elevator cage, said transmission device being separatedfrom said drive means and being responsive to off-center placement of aload in said cage for transferring forces from the less-loaded one ofsaid racks to the more-loaded one of said racks thereby to substantiallyequalize the loads on said two drive motors, said transmission devicecomprising an elongated third shaft spaced from each of said first andsecond shafts and extending between said pair of racks in parallelrelation to said first and second shafts, said third shaft being mountedfor rotation at a predetermined position on said elevator cage spacedfrom the location of said drive motors, the opposing ends of said thirdshaft respectively carrying third and fourth pinions which engage saidpair of racks respectively at positions spaced from each of said firstand second output pinions.
 2. The system of claim 1 includingselectively operable braking means in engagement with said transmissiondevice for selectively applying braking forces to each of said pair ofracks via said transmission device, thereby to distribute said brakingforces substantially equally to said pair of racks.
 3. The system ofclaim 2 wherein said braking means is operably responsive to the speedof movement of said elevator cage along said racks.
 4. The system ofclaim 1 including a sprocket wheel rigidly secured to said third shaftat a position between said third and fourth pinions, and a brakingdevice connected via a drive chain to said sprocket wheel forselectively braking said elevator cage.